<?php

include_once "errorCode.php";

/**
 * PKCS7Encoder class
 *
 * 提供基于PKCS7算法的加解密接口.
 */
class PKCS7Encoder {
	public static $block_size = 16;

	/**
	 * 对需要加密的明文进行填充补位
	 * @param $text 需要进行填充补位操作的明文
	 * @return 补齐明文字符串
	 */
	public function encode($text) {
		$block_size = PKCS7Encoder::$block_size;
		$text_length = strlen($text);
		//计算需要填充的位数
		$amount_to_pad = PKCS7Encoder::$block_size - ($text_length % PKCS7Encoder::$block_size);
		if ($amount_to_pad == 0) {
			$amount_to_pad = PKCS7Encoder::block_size;
		}
		//获得补位所用的字符
		$pad_chr = chr($amount_to_pad);
		$tmp = "";
		for ($index = 0; $index < $amount_to_pad; $index++) {
			$tmp .= $pad_chr;
		}
		return $text . $tmp;
	}

	/**
	 * 对解密后的明文进行补位删除
	 * @param decrypted 解密后的明文
	 * @return 删除填充补位后的明文
	 */
	public function decode($text) {
		$pad = ord(substr($text, -1));
		if ($pad < 1 || $pad > 32) {
			$pad = 0;
		}
		return substr($text, 0, (strlen($text) - $pad));
	}
}

/**
 * Prpcrypt class
 *
 *
 */
class Prpcrypt {
	public $key;

	public function __construct($k) {
		$this->key = $k;
	}

	/**
	 * 对密文进行解密
	 * @param string $aesCipher 需要解密的密文
	 * @param string $aesIV 解密的初始向量
	 * @return string 解密得到的明文
	 */
	public function decrypt($aesCipher, $aesIV = '') {
		try {
			$decrypted = openssl_decrypt($aesCipher, 'AES-128-CBC', $this->key, OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING, $aesIV);
		} catch (Exception $e) {
			return array(ErrorCode::$IllegalBuffer, null);
		}

		try {
			//去除补位字符
			$pkc_encoder = new PKCS7Encoder;
			$result = $pkc_encoder->decode($decrypted);
		} catch (Exception $e) {
			//print $e;
			return array(ErrorCode::$IllegalBuffer, null);
		}
		return array(0, $result);
	}
}
